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NAVAL
POSTGRADUATE SCHOOL
MONTEREY, CALIFORNIA
THESIS
Approved for public release; distribution is unlimited
NPS-SCAT: A CUBESAT COMMUNICATIONS SYSTEM DESIGN, TEST, AND INTEGRATION
by
Matthew P. Schroer
June 2009
Thesis Advisor: James H. Newman Second Reader: Terry E. Smith
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REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188) Washington DC 20503. 1. AGENCY USE ONLY (Leave blank)
2. REPORT DATE June 2009
3. REPORT TYPE AND DATES COVERED Master’s Thesis
4. TITLE AND SUBTITLE NPS-SCAT: A CubeSat Communications System Design, Test, and Integration 6. AUTHOR(S) Schroer, Matthew P.
5. FUNDING NUMBERS
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000
8. PERFORMING ORGANIZATION REPORT NUMBER
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10. SPONSORING/MONITORING AGENCY REPORT NUMBER
11. SUPPLEMENTARY NOTES The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government. 12a. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution is unlimited
12b. DISTRIBUTION CODE
13. ABSTRACT (maximum 200 words) Telemetry, tracking, and command (TT&C) systems on traditional small satellites
have advanced significantly in capacity, throughput, and complexity over the last several decades. The CubeSat community is in need of similar advancements. The Naval Postgraduate School Solar Cell Array Tester (NPS-SCAT) seeks to provide the foundation for advances in future iterations of CubeSats at NPS. This thesis explains the design, test, and integration of a full TT&C sub-system for NPS-SCAT. The satellite will have two TT&C systems that provide full telemetry for the experiment through a primary communications channel and secondary telemetry through an amateur band beacon. The thesis explains the development of the concept of operations for the satellite that drove the data requirements provided by the TT&C system. The thesis also explains the testing procedures of the transceiver and the design, test, and integration of the primary and secondary antennas. Finally the thesis explains the frequency licensing process through the Navy-Marine Corps Spectrum Center and the Federal Communications Commission.
15. NUMBER OF PAGES
222
14. SUBJECT TERMS Satellite, CubeSat, NPS-SCAT, solar cell tester, communications, antenna patch, dipole antenna, beacon, TT&C, frequency coordination, Navy-Marine Corps Spectrum Center
16. PRICE CODE
17. SECURITY CLASSIFICATION OF REPORT
Unclassified
18. SECURITY CLASSIFICATION OF THIS PAGE
Unclassified
19. SECURITY CLASSIFICATION OF ABSTRACT
Unclassified
20. LIMITATION OF ABSTRACT
UU NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18
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Approved for public release; distribution is unlimited
NPS-SCAT: A CUBESAT COMMUNICATIONS SYSTEM DESIGN, TEST, AND INTEGRATION
Matthew P. Schroer Captain, United States Marine Corps
B.S., United States Naval Academy 2000
Submitted in partial fulfillment of the requirements for the degree of
MASTERS OF SCIENCE IN SYSTEMS TECHNOLOGY (COMMAND, CONTROL, AND COMMUNICATION (C3))
and MASTER OF SCIENCE IN SPACE SYSTEMS OPERATIONS
from the
NAVAL POSTGRADUATE SCHOOL
June 2009
Author: Matthew Patrick Schroer
Approved by: James H. Newman Thesis Advisor
Terry E. Smith Second Reader
Dan C. Boger Chairman, Department of Information Sciences
Rudolph Panholzer Chairman, Space Systems Academic Group
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ABSTRACT
Telemetry, tracking, and command (TT&C) systems on
traditional small satellites have advanced significantly in
capacity, throughput, and complexity over the last several
decades. The CubeSat community is in need of similar
advancements. The Naval Postgraduate School Solar Cell
Array Tester (NPS-SCAT) seeks to provide the foundation for
advances in future iterations of CubeSats at NPS. This
thesis explains the design, test, and integration of a full
TT&C sub-system for NPS-SCAT. The satellite will have two
TT&C systems that provide full telemetry for the experiment
through a primary communications channel and secondary
telemetry through an amateur band beacon. The thesis
explains the development of the concept of operations for
the satellite that drove the data requirements provided by
the TT&C system. The thesis also explains the testing
procedures of the transceiver and the design, test, and
integration of the primary and secondary antennas.
Finally, the thesis explains the frequency licensing
process through the Navy-Marine Corps Spectrum Center and
the Federal Communications Commission.
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TABLE OF CONTENTS
I. INTRODUCTION ............................................1 A. THE GROWTH OF THE CUBESAT COMMUNITY ................1 B. THE NAVAL POSTGRADUATE SCHOOL SMALL SATELLITE
PROGRAM ............................................2 C. THE NAVAL POSTGRADUATE SCHOOL CUBESAT PROGRAM ......3 D. A BRIEF HISTORY OF CUBESAT COMMUNICATIONS SYSTEMS ..7
1. Pletsak Launch: June 30, 2003 .................7 2. Pletsak Launch: October 27, 2005 ..............8 3. Baikonur, Kazakhstan: July 2006 ...............9 4. Baikonur, Kazakhstan: April 2007 .............10 5. Satish Dhawan Space Centre, India: April 28,
2008 .........................................11 6. Separate Launches: CUTE 1.7 + APD and
GeneSat 1 ....................................12 7. Wallops, Maryland: June 2009 .................13
E. FUTURE CUBESAT COMMUNICATIONS SYSTEMS .............13
II. SOLAR CELL ARRAY TESTER COMMUNICATIONS SYSTEM REQUIREMENTS ...........................................17 A. DATA REQUIREMENTS .................................17
1. Data Overview ................................17 2. Solar Measurement System .....................18 3. Clyde-Space 1U Electrical Power Subsystem ....20 4. Temperature Sensors ..........................21 5. FM430 Flight Module ..........................22
B. SCAT CONCEPT OF OPERATIONS ........................22 1. Overview .....................................22 2. Start-Up Operations ..........................23 3. Normal Operations ............................24
a. Transmission Mode .......................25 b. Sun Mode ................................25 c. Eclipse Mode ............................28 d. Beacon Mode .............................28
C. POWER REQUIREMENTS ................................29 1. Primary Radio ................................29 2. Beacon .......................................30
III. RADIO DEVELOPMENT ......................................33 A. PRIMARY TT&C LINK .................................33
1. Basis for Radio Selection ....................33 2. MHX 2420 Specification .......................35 3. Primary Radio Link Budget ....................35
a. Propagation Path Length .................36 b. Free Path Space Loss ....................39
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c. Transmitting and Receiving Communications System Characteristics ...39
d. Energy per Bit versus Noise .............43 4. Radio Characterization and Testing ...........45
a. Current Draw Testing ....................45 b. Sensitivity Testing .....................53 c. Setting and Configuration Testing .......56
B. BEACON ............................................56 1. Specifications ...............................56 2. Link Budget ..................................58 3. Beacon Characterization and Testing ..........59
C. OTHER RADIO TESTING ...............................60 1. Field Testing ................................60
a. First Field Test ........................60 b. Test Antenna ............................60 c. Additional Planned Field Testing ........62
2. Maximum Data Rate Testing ....................66 3. Doppler Shift and Path Delay Considerations ..66
D. RECOMMENDED PRIMARY RADIO CONFIGURATIONS ..........67 1. Arbitrary Radio Settings .....................69 2. Radio to Input Interface Settings ............70 3. Radio to Radio Settings ......................71
IV. ANTENNA DESIGN .........................................75 A. ANTENNA DESIGN CONSIDERATIONS .....................75
1. Primary Radio ................................75 2. Beacon .......................................75
B. EARLY DESIGN CONCEPTS .............................76 C. ANTENNA DESIGN AND MODELING .......................77
1. Primary Radio ................................77 2. Beacon .......................................85
D. ANTENNA ANACHOIC TESTING ..........................94 1. Anechoic Chamber Background and Description ..94 2. Primary Antenna Anechoic Chamber Testing and
Results ......................................95
V. FREQUENCY COORDINATION ................................103 A. EARLY PROGRAM ASSUMPTIONS AND INITIAL FREQUENCY
WORK .............................................103 B. TRADITIONAL SMALLSAT AND CUBESAT FREQUENCY
COORDINATION MEASURES ............................104 1. PANSAT and NPSAT1 Frequency Coordination ....104 2. AMSAT Frequency Coordination ................105 3. NASA and Others Program Frequency
Coordination ................................106 C. THE FREQUENCY APPLICATION PROCESS FOR NPS-SCAT ...108
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1. Implications of Regulations for Federal Frequency Management on NPS-SCAT ............108
2. Frequency Request Process for NPS-SCAT Primary Radio ...............................112
3. Frequency Request Process for NPS-SCAT Beacon ......................................113
D. EXPERIMENTAL LICENSE APPLICATION .................113 1 Application Scenarios .......................113
a. DoD General Information ................115 b. Foreign Coordination General
Information ............................116 c. Transmitter Equipment Characteristics ..116 d. Receiver Equipment Characteristics .....117 e. Antenna Equipment Characteristics ......117
VI. CONCLUSIONS AND FUTURE WORK ...........................119 A. RADIO ............................................119
1. Primary Radio ...............................119 a. Conclusions ............................119 b. Future Work ............................120
2. Beacon ......................................121 a. Conclusions ............................121 b. Future Work ............................121
B. ANTENNA ..........................................122 1. Primary Radio Antenna .......................122
a. Conclusions ............................122 b. Future Work ............................122
2. Beacon Antenna ..............................123 a. Conclusions ............................123 b. Future Work ............................123
C. FREQUENCY COORDINATION ...........................124 1. Primary TT&C ................................124
a. Conclusions ............................124 b. Future Work ............................125
2. Beacon Frequency ............................125 a. Conclusions ............................125 b. Future Work ............................126
APPENDIX A. CONCEPT OF OPERATIONS NARRATIVE .............127
APPENDIX B. CONCEPT OF OPERATIONS VISUAL FLOW CHART .....131
APPENDIX C. MICROHARD MHX2420 SPECIFICATIONS ............139
APPENDIX D LINK BUDGETS ....................................141
APPENDIX E. SPECTRUM CONTROL INC., PATCH ANTENNA SPECIFICATIONS, DRAWINGS, AND MOUNTING PHOTO ..........145
APPENDIX F. NPS ANECHOIC CHAMBER SCHEMATIC ..............157
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APPENDIX G. TETHERS UNLIMITED INC., MICROHARD CONFIGURATION NOTES ...................................159
APPENDIX H. DD1494 AND FCC FORM 422 APPLICATIONS FOR GENESAT, KENTUCKY SPACE CONSORTIUM, AND NPS-SCAT ......163
LIST OF REFERENCES .........................................197
INITIAL DISTRIBUTION LIST ..................................203
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LIST OF FIGURES
Figure 1. First SSPL Adapter Concept (From Schulenburg, 2008, p. 8)......................................5
Figure 2. Second SSPL Adapter Concept (From Schulenburg, 2008, p. 8)......................................6
Figure 3. Sample I-V Curve................................18 Figure 4. NPS-SCAT Solar Panel Temperatures...............20 Figure 5. 2-D Satellite & Earth Center Geometry (From
Wertz & Larson, 1999, p. 113)...................37 Figure 6. Microhard Spectra 2420..........................46 Figure 7. Current Draw Test Setup.........................47 Figure 8. Python Serial Test Program Diagram..............49 Figure 9. MHX 2420 Current Test Transmit (1 Watt; 115200
bps)............................................50 Figure 10. MHX 2420 Current Test Idle (1 Watt;115200bps)...51 Figure 11. MHX 2420 Current Test Receive (1 Watt;
115200bps)......................................52 Figure 12. 2.4 GHz “Rubber Ducky” Antenna (From Pot, 2007).61 Figure 13. Big Sur Test Point Locations (From Google)......63 Figure 14. Mount Toro/Fremont Peak Test Point Locations
(From Google)...................................65 Figure 15. Circular Polarized Single Feed Patch
Arrangement (Feed Offset) (From Balanis, 2005, p. 862).........................................78
Figure 16. Circular Polarized Single Feed Patch Arrangement (Slot) (From Balanis, 2005, p. 864).79
Figure 17. Circular Polarized Single Feed Patch Arrangement (Trimmed Square) (From Balanis, 2005, p. 864)...................................79
Figure 18. CST Microwave Studio Modeled Patch, Part #PA28-2450-120SA......................................83
Figure 19. Patch Antenna Absolute Gain Pattern, Part# PA28-2450-120SA.................................84
Figure 20. Patch Antenna RHCP Gain Pattern, Part# PA28-2450-120SA......................................85
Figure 21. CP2 With Beacon Antenna Structure Visible.......86 Figure 22. Half-wave dipole normalized gain pattern........88 Figure 23. Half Power Beamwidth & Normalized Gain Plot.....88 Figure 24. NPS-SCAT Beacon Antenna and Structure...........93 Figure 25. NPS-SCAT Primary Radio Patch Antenna First Test
Article.........................................95 Figure 26. Mounted Patch Antenna VSWR Results..............96 Figure 27. First Patch Antenna Test Article Primary Gain
Figure 28. First Patch Antenna Test Article Rotated Gain Pattern.........................................97
Figure 29. NPS-SCAT Primary Radio Patch Antenna Second Test Article....................................99
Figure 30. Patch Antenna Mounted on CubeSat Primary Gain Pattern........................................100
Figure 31. Patch Antenna Mounted on CubeSat Secondary Gain Pattern........................................101
Figure 32. NTIA Geographic Regional Divisions (From National Telecommunications & Information Administration, 2008, p. 5-01).................109
Figure 33. NTIA Allocation Table for the Amateur Band (From National Telecommunications & Information Administration, 2008, p. 4-28).................110
Figure 34. NTIA Allocation Table for the ISM Band (From National Telecommunications & Information Administration, 2008, p. 4-39).................110
The amount of bandwidth the antenna can accommodate is
also an important consideration in the antenna design.
This is largely a function of the operating frequency, the
VSWR, and the length to twice the diameter ratio addressed
in the previous paragraph. Although charts are available
that can be used to estimate the approximate bandwidth for
a given length to diameter ratio, their use requires
significant empirical data and was outside the scope of
this thesis.
Based on the previously discussed requirements and
calculations, a preliminary dipole design for the beacon
antenna and the deployment structure was developed and is
shown in Figure 24.
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Figure 24. NPS-SCAT Beacon Antenna and Structure
Each element of the antenna will need to be the length
specified in Table 11. Additional tuning can also be
conducted once the antenna is installed to account for the
electro-magnetic interaction with the satellite. This
tuning should only be conducted once the flight model is
fully configured and there are no other planned changes in
the structure. The tuning will simply consist of cutting a
bit of antenna length from the radiating element to match
the network.
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D. ANTENNA ANACHOIC TESTING
1. Anechoic Chamber Background and Description
The purpose of testing antennas in an anechoic chamber
is to measure the antenna radiation patterns for each
antenna. The actual gain of the antenna is not measured
directly but is inferred from measuring the returns of the
test antenna and comparing them to the returns of a
reference antenna. The difference between the two antennas
is then subtracted from the gain of the reference to
calculate the gain of the test antenna (Broadston, 2009).
The receive antenna is linearly polarized while the antenna
to be tested is RHCP. This adds 3 dB of losses to the test
data, as well that will be accounted for in the plots.
The anechoic chamber at NPS is designed to measure
frequencies above 3 GHz. The design frequencies are
primarily driven by the size and composition of the
pyramidal radiation absorbent material (RAM) that lines the
chamber (Broadston, 2009). Though this introduces
inaccuracies into the measurement and pattern, it was the
best method available to test the antenna in a controlled
environment. There are additional inaccuracies introduced
from the layout of the chamber. Due to space limitations,
the anechoic chamber is not a perfect rectangle,
introducing additional reflections that are, nevertheless,
acceptable for measuring the pattern of the antenna. A
schematic drawing of the equipment is included in Appendix
F.
95
2. Primary Antenna Anechoic Chamber Testing and Results
The primary antenna testing was conducted in two
phases. The first phase consisted of testing the mounting
procedure of the antenna on a simple plastic backing. A
picture of the first test article is shown below.
Figure 25. NPS-SCAT Primary Radio Patch Antenna First Test Article
The antenna was first tested for its VSWR in the NPS
Microwave Lab. The VSWR was 1.67 at 2.44 GHz. The entire
VSWR test results are shown below.
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Figure 26. Mounted Patch Antenna VSWR Results
This was in line with the modeling and based on these
results the decision was made to proceed with a test in the
anechoic chamber. The anechoic chamber results are shown
in the following figures.
97
Figure 27. First Patch Antenna Test Article Primary Gain Pattern
Figure 28. First Patch Antenna Test Article Rotated
Gain Pattern
98
The measured pattern corresponds relatively well with
the modeled pattern. The maximum gain of the measured
pattern is 6.2 dB compared to 3.83 of the modeled antenna.
The increased directivity of the measured antenna is not
significant but can be attributed to differences in modeled
materials than those on the test article. The substrate,
Alumina, has different dielectric properties based on which
type is used. The model also provided a perfect electrical
connection between the ground plane that is incorporated
into the antenna design and the additional 45 mm by 45 mm
copper ground plane. Differences in the electrical
connection could reduce the fringing effects and thus
increase the directivity. Ultimately, the test article has
a front to back ratio of 12 dB, which is greater than the
modeled antenna but not unreasonable. Improved mounting
procedures, or the elimination of the copper ground plane,
could reduce the directivity and thus the front to back
ratio, increasing the antennas omni-directional
characteristics. Overall, the pattern of the first test
article was very similar to that of the modeled patch,
antenna and proved the validity of the modeling and the
fundamental mounting procedures for the patch antenna.
The second phase of testing was conducted with the
antenna mounted on the satellite frame in order to test the
mounting procedures for the flight article, and the gain
pattern that results from the interaction with the frame.
Because the mounting was similar to the first test article,
the antenna was quickly tested in the anechoic chamber.
While monitoring the test, observable results showed very
poor propagation characteristics that were more than 20 dB
less than measurements on the first test article. Several
99
variations of the test setup were attempted to correct the
problem. First, the boresight of the antenna to the
receiver was verified, the stability of the mount on the
satellite was verified, and the test receiver was verified.
Further examination showed that coax connection to the feed
pin on the antenna was loose and the solder was dislodged
and connecting intermittently. Additional stress relief
was implemented on the antenna mount using epoxy. After
the mounting was modified, the VSWR was checked using the
same procedure as the first test article. The VSWR was
1.62 at 2.40 GHz. This was in line with the first test
article and anechoic chamber testing was initiated. The
second test article is shown below.
Figure 29. NPS-SCAT Primary Radio Patch Antenna Second Test Article
100
The results from the second test article are shown
below.
Figure 30. Patch Antenna Mounted on CubeSat Primary Gain Pattern
101
Figure 31. Patch Antenna Mounted on CubeSat Secondary Gain Pattern
The test results show that the antenna maximum gain
increased to 6.8 dB for the patch antenna mounted on the
CubeSat aluminum skeleton. This is not a significant
change from the first test article. The front to back
ratio has increased significantly to 23 dB compared to 12
dB on the first test article. An increase in this value
was expected based on the increase in conducting material
directly behind the antenna. It would be useful to conduct
further analysis of the antenna pattern without the 45 mm
by 45 mm copper ground plane and simply rely on the ground
plane incorporated with the antenna and the satellite
structure. A graphical analysis of the pattern reveals
that that the maximum gain point, as well as the center
angle of the half power beamwidth is no longer at an normal
to the antenna face. This change in the pattern is logical
102
based upon the increased ground plane area in the form of
the CubeSat skeleton that is no longer evenly distributed
behind the patch antenna. The primary pattern has a
peculiar feature at 210 degrees. It was surmised during
the testing that this feature was indeed a null but was
also enhanced by a test artifact in the form of an
intermittent connection from the transmitter cabling to the
CubeSat Antenna. The null should not be this significant,
and there are irregularities at angles greater than where
the null occurs in the pattern, that suggest other
potential test artifacts. An important feature of the
pattern is a half power beamwidth of 110 degrees, which
also corresponds to the manufacturer literature.
103
V. FREQUENCY COORDINATION
A. EARLY PROGRAM ASSUMPTIONS AND INITIAL FREQUENCY WORK
When the NPS CubeSat team embarked on its initial
CubeSat design, it was assumed that the program would be
able to use similar equipment operating with the same
emissions as other CubeSat programs. Very little
documentation about CubeSat communications sub-systems
mentions frequency coordination. This assumption was also
based on the fact that the Microhard Radio is widely
marketed as a CubeSat communications solution by Pumpkin
Inc., and has been used by NASA in GeneSat and Pharmasat.
It was known that there were differences in frequency
allocation for civil and federal use, but since the
frequency had been used by NASA, it was assumed that NPS,
as a federal user would be able to use the same frequency.
Initial frequency coordination was accomplished by a
directed study student working with the FCC. The student
sought assistance based upon side note in the Microhard MHX
2420 Operating Manual. The note stated that the radio’s
EIRP could not exceed 36 dBm without FCC approval. Based
on preliminary link budgets it was known that the ground
station would have to exceed the EIRP threshold in order to
close the communications link. The student began
contacting the FCC to seek approval or an exception to the
rule in Part 15 of the FCC regulations. Shortly after
initial contact was made with the FCC, the student was re-
directed to the Navy-Marine Corps Spectrum Center (NMSC)
for further information. It was noted by the point of
104
contact that the only frequency coordinating authority that
the school should deal with is the NMSC.
B. TRADITIONAL SMALLSAT AND CUBESAT FREQUENCY COORDINATION MEASURES
Based on the mixed experiences of the directed study
student and the methods that NASA and others apparently
employed to receive frequency approval, further research
was undertaken into the frequency coordination process and
to document previous program’s efforts.
1. PANSAT and NPSAT1 Frequency Coordination
Since there was already an experienced employee at NPS
for satellite frequency coordination, research was first
conducted within the Small Satellite Program. Though there
are not any published papers on the frequency coordination
of PANSAT and NPSAT1, the personnel who effected the
coordination are still in the program and were available
for interviews. Mr. David Rigmaiden, the Small Satellite
Laboratory Manger was primarily responsible for the
frequency coordination of PANSAT and NPSAT1. PANSAT
operated at a frequency of 436.5 MHz, in the AM Band. The
program first attempted to coordinate frequency use through
the NMSC. However, when the NMSC adjudicated the request,
they allowed the school to directly contact and request
frequency approval through the FCC (Rigmaiden, 2009).
Approval to operate at 436.5 MHz was granted by the FCC.
NPSAT1 is significantly different from PANSAT in that
it does not use the AM Band for TT&C. Instead NPSAT1
utilizes 1767.565 MHz for uplink and 2207.3 MHz for its
downlink frequency (Sakoda & Horning, 2002, p. 7). Both of
105
these frequencies are within traditional space to earth and
earth to space operational frequency allocations for
federal use (National Telecommunications & Information
Administration, 2008, p. 4-36). In these specific cases
the frequencies are assigned to the U.S. Air Force
Satellite Control Network (AFSCN) (Rigmaiden, 2009). The
team was able to attain permission to operate on these
frequencies by coordinating directly with the AFSCN, and
then submitting a standard form DD1494, once informal
permission to operate had been granted, to formalize the
frequency allocation. The process for NPSAT1 could be
considered a more traditional government satellite
frequency assignment process as opposed to that used for
PANSAT (Rigmaiden, 2009).
2. AMSAT Frequency Coordination
Frequencies that reside within the portions of the
frequency band that are designated as the AM Band are
available for use by any amateur wishing to operate a
radio. The only governing body of these frequencies for
non-federal users is the Federal Communications Commission
(FCC). There exists an organization whose mission is to
promote the use of the amateur frequencies for satellite
communication in a responsible manner for the purpose of
educating amateur radio operators. The Radio Amateur
Satellite Corporation, or AMSAT does not manage any of
these frequencies, but provides support to the amateur
community for the efficient use of the frequencies. The
organization has several documents intended to support this
goal and educate the community regarding what is and is not
permissible in the AM band. Several of these restrictions
106
are applicable to the CubeSat community and must be
carefully examined in the context of each CubeSat Project
(The International Amateur Radio Union, 2006). There are
several critical restrictions that limit the use of the AM
band. They are that the purpose of the satellite must be
intended to either provide a communication resource for the
amateur community or provide self-training and technical
investigation relating to radio technique (The
International Amateur Radio Union, 2006). The operator of
the station must be serving solely for personal gain with
no pecuniary interest (The International Amateur Radio
Union, 2006). This eliminates many university programs
that would need to use funded staff or even students in
some cases to operate the ground station. The
communications over the AM band may not be concealed in any
manner (The International Amateur Radio Union, 2006). This
restricts encoding or encryption of the signal for anything
other than “space telecommand (The International Amateur
Radio Union, 2006, p. 8).” The most useful point of the
entire paper, from the perspective of NPS-SCAT, is the
direction given to apply for an experimental license if the
operator cannot meet the restrictions of an amateur license
and still wishes to operate in that portion of the
spectrum. Experimental licenses must be sought directly
through the FCC.
3. NASA and Others Program Frequency Coordination
Based on the knowledge gained from AMSAT and the
previous NPS satellite projects, a third area of frequency
licensing research was conducted in federal programs
operating in the AM or ISM bands and programs that had used
107
radios similar to those planned aboard NPS-SCAT. Chapter I
identified several NASA programs that used the MXH 2400
operating in the AM band, GeneSat and PharmaSat. There is
another program that used the MHX 2400 radio that was not
federally managed but was a private corporation, the MAST
satellite by TUI. An additional program that was
identified in the process of this research was the Kentucky
Space Grant Consortium and their KySat family of satellites
(Malphrus, 2009). The consortium owns and operates a 23
Meter parabolic satellite dish at Morehead State Space
Science Center that is using a Microhard MHX2400 to provide
primary telemetry to KySat. The frequency request process
associated with the NASA satellites and the others is
different. Based on the NTIA, federal agencies such as
NASA should seek experimental licenses for their CubeSat
applications through the Office of Spectrum Management
(OSM) which resides within the NTIA (National
Telecommunications & Information Administration, 2008, p.
8-1). The non-federal users should seek experimental
licenses through the FCC. Both the OSM and FCC are
governed by an overarching frequency management document
that specifies what frequencies can be used for what and by
whom published by the Department of Commerce. The document
is the Manual of Regulations and Procedures for Federal
Radio Frequency Management and it is derived from federal
code and international agreements governing frequency usage
(National Telecommunications & Information Administration,
2008, p. 3-1). In reality, NASA did not acquire the
license for GeneSat or PharmaSat. The license holder is a
Mr. Michael Miller with Intellus who was contracted by
Santa Clara University, the operator of the ground station
108
(Miller, 2009). Because the ground station and the primary
telemetry link of the satellite are licensed by a non-
federal entity, Santa Clara University and Mr. Michael
Miller, they are not subject to the same licensing
procedures as federal entities, which would normally apply
to organizations such as NASA and NPS. The procedure used
for GeneSat and PharmaSat is applicable to both the MAST
satellite from TUI and the Kentucky Space Grant Consortium
23 meter ground station. The entities requested an
exception to the emission and operator restrictions imposed
on the AM Band and operate under an experimental license
granted by the FCC. In the case of the Kentucky Space
Grant Consortium, Mr. Michael Miller was contracted as well
to expedite and hold the experimental license (Malphrus,
2009).
C. THE FREQUENCY APPLICATION PROCESS FOR NPS-SCAT
1. Implications of Regulations for Federal Frequency Management on NPS-SCAT
As discussed earlier in this chapter, there exists an
overarching document that governs frequency usage for
federal and non-federal entities within the United States
and worldwide. Many of these regulations are applicable to
the NPS-SCAT program, some of which restrict the program’s
ability to request a frequency, and others give the program
direction on which path to pursue. The first critical
restriction is the use of the specific frequencies. The
table headers first divide the frequency allocations into
international and United States as shown in the
accompanying figure. The international segment is then
divided into three regions based on the area of the world
shown below.
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Figure 32. NTIA Geographic Regional Divisions (From National Telecommunications & Information
Administration, 2008, p. 5-01)
The United States is divided into federal and non-
federal users. Once a user has identified their region or
their user category the specific uses for their frequency
of interest can be identified. In the case of NPS-SCAT the
beacon operates in the 430 MHz range and the primary radio
operates in the 2.44 GHz range. Based on Chapter 8,
Paragraph 2.17 of the NTIA regulations, NPS is considered a
Federal Station. The following figures show the
delineation of these frequency ranges by the NTIA for both
frequency ranges.
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Figure 33. NTIA Allocation Table for the Amateur Band (From National Telecommunications & Information
Administration, 2008, p. 4-28)
Figure 34. NTIA Allocation Table for the ISM Band (From National Telecommunications & Information
Administration, 2008, p. 4-39)
The table shows that the use of the frequencies from
420-450 MHz is allowed for non-federal amateurs but is
restricted to radiolocation for federal users with
footnotes of US217, G2, and G219. In this case the
footnotes are not applicable to the applications required
for NPS-SCAT and further define the ability to operate
radiolocation devices in that frequency band. The second
table shows that the frequencies from 2417-2450 MHz are
reserved for radiolocation in the federal allocations and
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for amateur use in the non-federal allocations. The FCC
Rule Part(S) Remarks column states that the equipment in
operation in that portion of the band must comply with the
Industrial, Scientific, and Medical (ISM) band restrictions
and the AM band restrictions, which are contained in Parts
18 and 97 respectively of the FCC Code. The ISM code
restricts non-licensed devices operating in those
frequencies to an EIRP of 36 dBm or less. Based on this
restriction, the other CubeSat programs that have used ISM
devices as their radio must still seek an experimental
license, because a ground station with a EIRP of 36 dBm or
less is not likely to close the link. In the case of
GeneSat, PharmaSat, and MAST; the 60 foot parabolic mesh
antenna at Stanford Research Institute (SRI) was used
initially as the ground station (Newton, 2009). In order
to create a wider beamwidth, only a 10 meter diameter area
of the dish was illuminated, but that would still generate
an EIRP of 42 dBm (Mas & Kitts, 2007, p. 5). Based on the
EIRP, the ground station does not conform to the ISM
restrictions and would still require an experimental
license to operate. The Kentucky Space Consortium antenna
has an ever greater EIRP at nearly 50 dBm and would need
the same licensing as SRI. In the process of researching
previous work many of these experimental licenses were
acquired and are included in Appendix H.
Though experimental licenses do allow for additional
flexibility when operating a radio in a frequency other
than what it is regulated for, there are still conditions
imposed on experimental stations and those are outlined in
Title 47, Part 5 of the Code of Federal Regulations (CFR).
For the purposes of NPS-SCAT, the CFR permits stations
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operating in the Experimental Radio Service to conduct
“Communications essential to a research project”
(Government Accounting Office, 2009, Title 47, Part 5.51).
2. Frequency Request Process for NPS-SCAT Primary Radio
Based on the discussion in the previous section, the
type of license required for the primary radio on NPS-SCAT
seemed clear. An experimental license would be required to
operate COTS equipment in the ISM Band, by a federal user,
with an EIRP exceeding 36 dBm. The team continued the work
that was completed by the directed study student, and
initiated further dialogue with the NMSC. The initial
response of the NMSC was that the program could not use
frequencies in the ISM band because it was considered a
federal user. After a lengthy discourse with the NMSC,
that was elevated to the Office of the Chief of Naval
Operations N6 and lasted several months, the determination
was made that the NPS-SCAT could apply for the use of the
amateur frequency under an experimental license. NPS-SCAT
was directed to apply for an experimental license directly
to the FCC using the FCC Form 422. The application was
submitted to the FCC on 31 March 2009 and returned the next
day as denied without prejudice. Further conversation with
a representative from the FCC clarified the problem with
the application. The FCC views the application as a method
to assign liability, in the case where the radio interferes
with another emitter that has priority to operate within
that portion of the band. Based on this viewpoint, and the
fact that NPS is part of the Department of the Navy, the
application must first be submitted in whole to the NMSC,
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approved, and then routed to the FCC for final approval.
This process assures that the Department of the Navy has
complete cognizance over radios operating outside of normal
parameters and is prepared to assume responsibility in case
there are any problems with liability. Because the NMSC
does not deal with FCC forms, the NPS-SCAT team was
directed to submit a DD1494 for the licensing process. The
DD1494 is the standard licensing document used by the NMSC
and the Joint Spectrum Center.
3. Frequency Request Process for NPS-SCAT Beacon
The frequency request process appears simple but
became complex as explained earlier in the previous
paragraph. Based on this experience, a different path was
sought to license the beacon. Cal Poly assumed the
responsibility to license the beacon as well as build it.
Their standing as a non-federal user, simplified the
overall process, and reduced the interaction required with
the licensing authority to the FCC. Based on this
licensing arrangement, Cal Poly will control the beacon and
the emissions associated with it, and NPS personnel can
only receive the transmitted data like any other amateur
radio operator.
D. EXPERIMENTAL LICENSE APPLICATION
1 Application Scenarios
The experimental license application was developed for
two scenarios. The first scenario included the use of the
MHX 2420 radio. Though this radio was not desired, it
could function given a more capable EPS that could be
available aboard NPS-SCAT++ or other variants of the NPS-
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SCAT standard sub-system design. The second scenario
developed a license request for the MHX 2400. The
licensing plan with two contingencies was developed because
there remained a possibility that the MXH 2400 could be
procured even though the radio was no longer actively
manufactured by Microhard. If the MHX 2400 is procured, the
NPS-SCAT team will conduct the same series of tests as were
conducted on the MXH 2420 and described in Chapter III.
The tests will allow the team to validate the viability of
the radio and submit a license application based on the
performance of both radios.
2 DD1494 Explanation
Completed applications for both scenarios have been
generated and are included in the thesis Appendix H. The
Joint Spectrum Center has developed software named EL-CID
that automates the licensing application by generating
database. The actual DD1494 was completed with this
software and electronic copies of the application database
are maintained on the Small Satellite Laboratory server.
Because characterization testing was conducted on the MHX
2420, the full explanation of an experimental license
application will use the first scenario described in the
previous paragraph for the MHX 2420. A significant portion
of the application was provided by the radio manufacturer,
Microhard Systems Inc., through the DD1494 that was
originally submitted for approval to the Joint Spectrum
Center. The portions provided in that DD1494 that are
applicable to this application will not be explained, only
the exceptions. The original DD1494s provided by Microhard
Systems Inc. are included in Appendix H. The application
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is divided into five sections, DoD General Information,
Foreign Coordination General Information, Transmitter
Equipment Characteristics, Receiver Equipment
Characteristics, and Antenna Equipment Characteristic.
a. DoD General Information
The DoD General information is intended to
identify the originating agency of the licensing request.
The originating address on the applications is the NPS
Small Satellite Laboratory. Block 4 is not applicable to
the program because it is completed in subsequent pages for
the receive and transmit modes of the radio. Block 5,
Target Starting Date For Subsequent Stages, shows that
Stage 2, or the experimental stage is planned to start on 1
April, 2010. This is based on an expected launch date for
the satellite. Because this form is not designed for an
experimental license, like the FCC Form 422, the other
stages are not applicable to this application. Block 6,
extent of use, is based upon a normal day of passes by NPS-
SCAT in the ground field of view based on the previously
described orbitology. Block 7, is not applicable because
it is documented in the geographic area documentation for
each station. Block 8, 2 unites used in Stage 2, is based
on the number of units operating in the same environment.
In the case of NPS-SCAT or SCAT++, there will only be two
units operating simultaneously because of the constraints
of a single ground station. The remarks in Block 13 are
included to mitigate the requirement to coordinate the
satellite frequency use with the Radiocommunications Bureau
of the International Telecommunications Union.
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b. Foreign Coordination General Information
Block 6 of this page is the first unique item to
the application. The block, entitled “purpose of system,
operational and system concepts,” describes the concept of
operations for the satellite. It is a brief summary of
Chapter II of this thesis. The block also describes the
Federal Code that allows radios to operate in the
experimental service. This part of the code is what
provides NPS-SCAT the justification to operate with an
experimental license. Block 7 of this page outlines the
data requirements of the satellite as described in the data
budget portion of this thesis. Also included in Block 7
are operating characteristics of the radio, the frequencies
it operates within and the ability to lock out specific
frequencies.
c. Transmitter Equipment Characteristics
Much of the transmitter equipment characteristics
are the same as those in the Microhard Systems Inc. DD1494
that was provided to the NPS-SCAT Team by Microhard Systems
Inc.. There are additional items required on the
application that were obtained through a dialogue with the
Microhard Technical Support Office. Typically, the
transmitter and receiver equipment characteristics would be
a single system for each if they are the same equipment at
both locations. However, the ground station for NPS-SCAT
will include an additional High Power Amplifier (HPA) that
modifies the power output of the transmitter. Based on
this, two types of transmitters were included in the
application for the different transmitted powers. The
first block that deviates from the Microhard DD1494 is
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Block 13, Maximum Bit Rate. Block 13 is listed as 19200
bps based on the slowest bit rate available on the MHX
2420. This requirement is explained earlier in the thesis.
Block 19.a, the Mean Power is also different for the
transmitter at the ground station. This is listed as 10.0
Watts based on the HPA capabilities for the ground station.
d. Receiver Equipment Characteristics
The receiver equipment characteristics are the
same as those in the Microhard MHX 2420 DD1494 with the
exception of Block 16, maximum bit rate. Because NPS-SCAT
will operate at 19200 bps, that is the bit rate listed in
Block 16.
e. Antenna Equipment Characteristics
The antenna equipment characteristics are
independent of the Microhard radio system used for NPS-
SCAT. The parameters are based on the characteristics of
the NPS Ground Station configured by Luke Koerschner and
documented in the thesis listed in the bibliography and the
testing conducted for this thesis on the patch antenna for
NPS-SCAT. For the NPS Ground Station, all the parameters
required for the application are included in Luke
Koerschner’s thesis and are listed in the DD1494 included
in the Appendix H. For the satellite antenna equipment,
most of the information can be extracted from Chapter IV of
this thesis. Important points in the applications are
Block 8.a, Main Beam Gain, which is listed at 4.20 dBi and
Block 8.b, First Major Side Lobe Gain, listed as -21.8 dBi.
Also included are the beamwidths of 110 degres which were
discussed previously.
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VI. CONCLUSIONS AND FUTURE WORK
A. RADIO
1. Primary Radio
a. Conclusions
The testing conducted on the MHX 2420
demonstrated that it is not a good candidate given the
limitations of a 1U EPS typical in CubeSats. This is
primarily based on the current draw and power consumption
of the radio. The form factor of the device is ideal for
the requirements of a CubeSat and a radio of similar
capabilities, with a similar form factor, and lower current
draw would be an excellent candidate for future CubeSat
implementation. Until a better radio is introduced, the
best option for the program is to procure MHX 2400s for
operation in the satellite. The MHX 2400s have been tested
and documented by NASA and would provide the means to
complete the NPS-SCAT mission until better products are
available.
A valuable lesson learned during the testing
process is that testing should begin at fundamental level,
isolating unknown variables and then extend into
environments where unknown or uncontrolled variable are
introduced. In the case of the testing on the MHX 2420,
testing in the outdoor environment should have been
balanced with laboratory testing. The tests that
characterized the fundamental aspects of the radio should
have then been followed by more in depth testing of the
effects of radio settings in a quiet RF environment;
conducted concurrently with tests in a terrestrial setting.
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b. Future Work
If the program is able to procure MHX 2400s,
testing similar to that described in Chapter III should be
conducted on the radios. Following the fundamental
characterization of the radio, more in depth optimal
setting research should be conducted depending on the
differences from the MHX 2400 to the MHX 2420. Finally, an
improved set of terrestrial tests should be conducted.
These tests should attempt to elevate the slave radio above
ten degrees elevation from the ground station. The tests
should utilize both directional horn antennas as well as
the NPS-SCAT prototype antenna. The terrestrial tests
should be conducted in several phases. The first phase
would simply be MHX 2400s transmitting to each other at
distances from 1 to 60 Km. The distances that can be
tested will vary because the radios require line of sight
in order to communicate. A good plan for testing in the
Monterey Peninsula is included in Chapter III of this
thesis. The second phase would incorporate the ground
station transmitting to a slave radio serving as the
satellite at various distances. The third stage would
resemble the final launched version of the satellite, with
an MHX 2400 in the NPS-SCAT prototype transmitting through
the primary antenna. Throughout all the tests Bit Error
Rate should be measured as well as realized throughput.
Finally, the ground station remains to be built
and integrated. The fundamental structure for the ground
station is in place, but there is a significant amount of
work to integrate an MHX radio, integrate and test the High
Power Amplifier and Low Noise Amplifier, develop an
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automation of operations scheme, develop a database
management plan, and test the completed system.
2. Beacon
a. Conclusions
The choice to implement a beacon into NPS-SCAT
was timely. Though an additional communications sub-system
introduces more workload, the risk mitigation that it
provides for the overall system as well the enhancements
that it provides to the concept of operations makes it
worthwhile.
b. Future Work
The beacon system has a significant amount of
work remaining. The beacon development board has been
constructed but the flight article and final integration
plan has yet to be finalized and will need to be
incorporated into the satellite. The beacon ground station
at NPS is in the midst of a repair, and like that of the
primary radio, will need to be re-integrated with a
transceiver, an automation scheme developed, and the system
tested. Because the data to be downlinked has a relatively
low refresh rate, an automated database is not necessary
but could be incorporated. Over the long term, it will be
useful to begin an iteration on the next generation of
beacon design or firmly establish a relationship with a
beacon provider such as Cal Poly.
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B. ANTENNA
1. Primary Radio Antenna
a. Conclusions
The primary radio antenna selection process
worked out well. The antenna that was purchased was a good
fit for the program and the form factor. The difficult
portion of the antenna development was the mounting and the
testing. The mounting diagrams provided by the
manufacturer in appendices are ambiguous and not well
described. The mounts that were used for testing were
largely trial and error and as a result were sub-optimal.
This was also a result of the author’s antenna mounting
experience. Given more assets and time, it would be
worthwhile to conduct several practice antenna mountings
before attempting mounting an antenna for test. The value
of a high-quality mount cannot be understated and can save
a significant amount of time in the end. In the case of
this thesis, three weeks of test time would have been
saved.
b. Future Work
Much of the work for the primary antenna has been
completed. Future work should include refining the
mounting procedure to further reduce the VSWR. Also, tests
should examine the value of the 45 mm by 45 mm ground plane
against only using the ground plane provided by the antenna
itself. It is an interesting thought to eliminate the
ground plane, and thus reduce the directivity of the
antenna, producing a more omni-directional antenna. The
reduction of the ground plane might also add additional
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placement options or increase the amount of surface area
available for solar cells. Finally, testing should be
conducted on a completed solar panel with the antenna
mounted. Conducting a final characterization of a
completed panel would serve as an assurance that the
pattern is acceptable for operations on orbit.
2. Beacon Antenna
a. Conclusions
The fundamental aspects of the beacon antenna
have been completed. The design is simple but will require
fine tuning upon the integration with the beacon. Because
a half-wave dipole design is well documented, there are no
significant conclusions for this portion of thesis.
b. Future Work
Future work for the beacon includes the
construction of the actual antenna. The deployment device
will also have to be designed, though it is simple and well
documented throughout the CubeSat community. Finally, the
antenna will need to be tested. Unfortunately, there is
not an anechoic chamber at NPS for the frequencies that the
beacon will operate within. Unless an anechoic chamber can
be located, a test similar to one conducted on the PANSAT
antenna will have to suffice to characterize the gain in
the far field. VSWR testing may also be conducted which is
extremely valuable as demonstrated through the testing on
the primary antenna.
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C. FREQUENCY COORDINATION
1. Primary TT&C
a. Conclusions
The AMSAT paper referenced in Chapter V leads off
with sage advice regarding satellite communications, start
the frequency coordination process as soon as possible.
Generally this means during the development process of the
radio. If a COTS item is the preferred solution, then the
frequency research would begin during the process of
researching potential products. If nothing else can be
gained from the frequency coordination narrative, it should
be that it is not a simple process. Based on obstacles
encountered and the experience of the author coordinating
frequencies in the operational forces, it might be valuable
for NPS to explore a frequency manager position. A full
time expert operating within the institution’s framework
would significantly simplify the task, would enhance the
corporate knowledge of the frequency coordination process,
and would help formalize the relationship between NPS and
the NSMC. Without a dedicated individual, the process will
likely be re-invented every time a frequency is required,
because the frequency of any individual seeking a frequency
is low. Even if a more permanent frequency manager
position is not established a more formal process and
regular point of contact must be established at the NMSC in
order to alleviate the burden of requesting and
coordinating a frequency for every application.
The complexity of requesting an experimental
license, as well as the NMSCs reluctance to allow an
experimental license application to proceed, demonstrates
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the value of operating within the bands normally allocated
for satellites, as documented within the NTIA regulations.
In the future, if a radio can be built or bought and tuned
to these frequencies, its value should be thoroughly
explored against the value of a COTS radio operating in the
ISM or amateur band.
b. Future Work
Once the actual system is finalized the only
frequency coordination work remaining is to submit the
application. As mentioned in the previous paragraph, there
are several actions that could be initiated to simplify
this process for future projects. Another avenue that
should be explored is requesting that NPS be added to the
list of experimental station in Chapter 7 of the NTIA
regulations. These stations are permitted to use any
frequency for “short or intermittent periods without prior
authorization of specific frequencies (National
Telecommunications & Information Administration, 2008).”
Base on the testing and experimentation at NPS and the
other stations listed on the exemption this seems like a
logical path. The only obstacle may be the requirement of
a frequency manager to support the experimental station
designation, though the value of this designation would far
exceed the cost of a dedicated frequency manager.
2. Beacon Frequency
a. Conclusions
Based on the restrictions to operate in the
amateur band, the NPS-SCAT team cannot take any action to
request an amateur license to operate a beacon. Because of
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this, the only option is for a non-federal collaborator to
build the beacon and coordinate the frequency for its
operation. In this light, a partnership with Cal Poly is a
great opportunity for both parties and allows for risk
mitigation of a critical subsystem for future CP satellites
and allows NPS satellites to broadcast using a Cal Poly
radio operating with a legitimate amateur license.
b. Future Work
There is not much opportunity for future work on
beacon frequencies. Unless an overall exemption to the
NTIA licensing requirements may be obtained, as described
earlier, NPS will never be permitted to use a transmitter
on orbit operating in the amateur band without an
experimental license. Again, this restriction and the
ability to overcome it, demonstrates the value of a
dedicated frequency manager to the entire school.
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APPENDIX A. CONCEPT OF OPERATIONS NARRATIVE
Assumptions: - Approximately 92 minute orbit period
- 56 minutes in eclipse and sunlight each
- Data values for current and voltage measurements need to only be 16 bit floats
- Abbreviated Telemetry (includes system health and 15 point IV Curve) is between 154 and 242 bytes depending on SLIP characters
- Full Telemetry (includes historical system health, 100 point IV curve, temperature and sun angle) is between 494 and 922 bytes
- System Health is defined as current draw for each subsystem, battery voltage, temperature, and count of watchdog timer resets
- Historical System Health is defined as System Health that is sampled once during an operational period for each operating mode
- An operational period is defined as the timeframe from one primary TT&C downlink to the next
- There are four operational modes:
o Sun Mode – The generation of IV Curves for each experimental solar cell, temperature, and sun angle.
o Eclipse Mode – The mode active during which there is no voltage generated by the power cells and minimum systems are functional
o Transmission Mode – The broadcast of Full Telemetry and active communication with the ground station
o Beacon Mode – The broadcast of Abbreviated Telemetry using a simplex communication link, transmitting every two minutes for 30 seconds
Operational Timeline: - Launch
o NPS-SCAT is launched from SSPL via NPS-SCAT++ OR from P-POD
o Four hour timer is initiated to ensure batteries are fully charged prior to commencing operations; FM430 is powered on after launch
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- Start-up Operations
o Verify battery voltage is within required tolerance
o If battery voltage is within tolerance, then NPS-SCAT will commence Normal Operations
o If the batteries are not within tolerance, timer will be reset for 4 hours and repeat Start-up Operations
o If Start-up Operations has been cycled three times and the battery voltage is not within tolerance, then NPS-SCAT will commence Normal Operations
- Normal Operations
o Check for power generated from solar cells
If power is being produced (i.e. NPS-SCAT is in the sun):
If power is produced by the z-axis solar cells, the positive and negative z-axis temperature sensors will be compared
If the positive z-axis is warmer (i.e., sun is shining on experimental solar panel), enter Sun Mode
Fifteen minute timer will be activated. Taking one full I-V curve every 15 mins.
If power is not produced (i.e., NPS-SCAT is in eclipse):
Enter Eclipse Mode
o If a ground transmission is received, any ongoing operations will be interrupted and NPS-SCAT will enter Transmission Mode.
Upon completion of necessary communications, NPS-SCAT will be directed to return to Normal Operations.
o Beacon Mode will be continuously active
Data Analysis: Based upon the above orbital assumptions and preliminary data packet size, the worst case required downlink time over the ground station was calculated to be 129 seconds per week. As per the CONOPS:
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Primary Telemetry (MHX2420): Each Full Telemetry message (including full 100 point IV Curve, temperature, sun angle, and system health) is between 764 and 1264 bytes. Number of Watchdog Timer Resets: 15-19 Bytes 15 Temperature Measurements: 225-285 Bytes Sun Angle: 21-31 Bytes Battery Temp, Current Voltage: 90-114 Bytes 100 Point IV Curve: 413-815 Bytes TOTAL: 764-1264 Bytes For the most probable case (approximately 764 bytes per message), there will be three IV Curves and other data generated per orbit resulting in 2292 bytes of data per orbit. There are approximately 16 orbits per day resulting in 36672 bytes generated per day. The primary telemetry will be transmitted at an interval not to exceed one week which will result in 256704 bytes available for downlink. Using the MHX2420 lowest data rate available of 19200 bps (2400 Bytes per second) would result in a total downlink time of 106 seconds For the worst case (approximately 1264 bytes per message), there will be three IV Curves and other data generated per orbit resulting in 3792 bytes of data per orbit. There are approximately 16 orbits per day resulting in 60672 bytes generated per day. The primary telemetry will be transmitted at an interval not to exceed one week which will result in 424704 bytes available for downlink. Using the MHX2420 lowest data rate available of 19200 bps would result in a total downlink time of 176 seconds. Downlink time will be shorter since downlink will be in shorter intervals, with fewer SLIP characters and a potentially higher data rate. Secondary Telemetry (Beacon): Each Abbreviated Telemetry message (including abbreviated IV Curve, temperature, sun angle, and system health) is between 424 and 584 bytes. The abbreviated IV Curve and System Health will be broadcast continuously during the active period of the transmitter.
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APPENDIX B. CONCEPT OF OPERATIONS VISUAL FLOW CHART
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APPENDIX C. MICROHARD MHX2420 SPECIFICATIONS
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APPENDIX D LINK BUDGETS
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APPENDIX E. SPECTRUM CONTROL INC., PATCH ANTENNA SPECIFICATIONS, DRAWINGS, AND MOUNTING PHOTO
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APPENDIX F. NPS ANECHOIC CHAMBER SCHEMATIC
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APPENDIX G. TETHERS UNLIMITED INC., MICROHARD CONFIGURATION NOTES
For MAST, we had what I referred to as two different types of radio parameter sets: stuff that never changed and was hard-coded in the software and stuff that was configurable post-launch. For the stuff that never changed, there was a hard coded sequence of commands sent in the following order (this was an array of strings in program memory): "E1", // Command Echos: 0=disable command echos, 1=enable command echos "Q0", // Quite Mode: 0=enable results, 1=disable results "V1", // Verbose Responses: 0=responses as numbers, 1=responses as words "W0", // Connection Result: 0=CONNECT xxxx, 1=CARRIER xxxx, 2=CONNECT xxxx "&C1", // DCD: 0=always on, 1=on when synchronized, 2=output data framing, 3=sync pulse "&D2", // DTR: 0=ignored, 2=force command mode, 3=resets modem "&K3", // Handshaking: 0=disabled, 2=RTS/CTS input framing, 3=enabled "&S1", // DSR: 0=always on, 1=on in data mode only, 2=DSR/DTR signaling "&E0", // Framing Errors: 0=disable checking, 1=enable checking "S0=0", // Auto Answer: 0=power up in command mode, 1=power up in data mode "S2=43", // Escape Code: 43='+' set to default and known value "S3=13", // Carriage Return: set to default and known value "S4=10", // Line Feed: set to default and known value "S5=8", // Backspace: set to default and known value "S101=3", // Operating Mode: 1=Master P-M, 2=Master P-P, 3=Slave, 4=Rpeater, 5=Master Diagnostics "S109=7", // Hopping Interval: unused in slaves but set to known value, 7=80msec "S110=1", // Date Format: 1=8N1, 2=8N2, 3=8E1, 4=8O1, 5=7N1, 6=7N2, 7=7E1, 8=7O1, 9=7E2, 10=7O2, 11=9N1 "S113=0", // Packet Retransmissions: unused in slaves, but set to known value "S117=0", // Modbus Mode: 0=disabled, 1=enabled "S119=1", // Quick Enter to Command: 0=disabled, 1=enabled "S120=0", // RTS/DCD Framing Interval: unused without input framing, but set to known value "S121=0", // DCD Timing: unused without input framing, but set to known value "S122=1", // Remote Control: 0=disabled, 1=enabled "S124=0", // TDMA Duty Cycle: unused in slaves, but set to known value "S125=0", // TDMA Max Address: unused in slaves, but set to known value "S126=0", // Data Protocol: 0=Transparent IN/OUT "S127=1", // Address Filtering: 0=disabled, 1=enabled "S128=1", // Multicast Association: 0=65535 only, 1=0 and 65535 "S129=0", // Secondary Master: unused in slaves, but set to known value "S206=0", // Secondary Hopping Pattern: unused in slaves, but set to known value
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For the stuff that was configurable post-launch, these are the defaults that we used: - output power (we intelligently varied this between 250mW and 1W based on current battery charge level because we were having voltage regulator dropouts at the higher output powers when the battery was more discharged) - minimum packet size: 6 bytes (this was our minimum frame size for our messaging protocol) - maximum packet size: 100 bytes (I think I remember increasing this to 255 during operations to increase overall throughput) - packet size control (S114) (I don't remember what this means, but we defaulted to NOT overriding) - packet buffer timeout: 250ms - packet retry limit: 4 - packet repeat interval: 1 - network address: arbitrary - unit address: arbitrary - encryption key: arbitrary - slave roaming: enabled
1. Slave Roaming a. When enabled, a slave will scan other hopping
patterns while attempting to synchronize with a master. In essence, it will tune to the hopping pattern of any communicating a master.
b. Results i. When enabled, synchronization is possible
regardless of the slave’s hopping pattern. The synchronization process is noticeably (albeit not by much) faster when the hopping patterns are set to the same pattern.
ii. When disabled, synchronization is only possible when the master’s hopping pattern matches that of the slave. Synchronization appeared a little slower than when roaming was enabled and the hopping patterns matched. Also, the master was unable to synchronize with the slave even if its hopping pattern was within the same group.
iii. The manual states that the master must be using a hopping pattern from the same group for the roaming slave to tune to the master. This statement seems to be false as the slave would synchronize with the master even if the slave’s hopping pattern was in an entirely different group than the master’s.
c. Implications
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i. Allowing the slave to roam in a noisy and low link margin environment with other transmitting masters, will likely increase the time in which it takes to synchronize to a slave.
ii. If roaming is disabled, and a single event upset changes the hopping pattern of the slave and goes unnoticed by the flight software, then communication will be impossible. Each pattern would need to be scanned by the master in an attempt to find the slave.
2. Hop Interval a. Results
i. Very short hop intervals made synchronization impossible. The hopping interval should be at least 20msec to allow synchronization to succeed. Synchronization was possible at every hopping interval greater than and equal to 20msec.
3. Address Filtering and Multicast Association a. With both of these enabled, a slave can receive
data if its unit address does not match that of the master and if the unit address of the master is 0 or 65535. For the slave to transmit, its unit address must match that of the master.
b. Implications i. Both of these should be enabled as it will
allow the slave to receive packets (and thereby the flight software can receive commands) even if a single event upset alters the slave’s unit address.
4. Point-to-Multipoint vs. Point-to-Point a. Synchronization appears to be much quicker when
the master is configured as a point-to-multipoint than when it is configured as a point-to-point.
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APPENDIX H. DD1494 AND FCC FORM 422 APPLICATIONS FOR GENESAT, KENTUCKY SPACE CONSORTIUM, AND NPS-
SCAT
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QUESTION 6: PURPOSE OF EXPERIMENT
6. * Is this authorization to be used for providing communications essential to a research project? (The radio communication is not the objective of the research project)? If "YES", include as an exhibit the following information: a. A description of the nature of the research project being conducted. b. A showing that the communications facilities requested are necessary for the research project. c. A showing that existing communications facilities are inadequate. NOTE: When submitting this exhibit, please enter "QUESTION 6: PURPOSE OF EXPERIMENT" in the description field and select the type of document as "Text Documents".) ANTENNA DRAWING: Submit as an exhibit a vertical profile sketch of total structure including supporting building, if any, giving heights in meters above ground for all significant features. Clearly indicate existing portion, noting particulars of aviation obstruction lightly already available. Submit this sketch under the "Antenna Drawing" exhibit type. NECESSARY BANDWIDTH DESCRIPTION Please indicate the necessary bandwidth measurement and indicate the units by selecting one of the values in the
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drop-down list. Submit an exhibit describing how the necessary bandwidth was calculated for all the indicated frequencies. Exhibits may be entered immediately after submitting this form or later by selecting the "Add Attachments" option from this web site's menu. NOTE: When submitting this exhibit, please enter "NECESSARY BANDWIDTH DESCRIPTION". in the exhibit description. MODULATING SIGNAL DESCRIPTION (entered “BPSK”) Insert as appropriate for the type of modulation (e.g. The maximum speed for keying in bauds, maximum audio modulating frequency, frequency deviation of carrier, pulse duration and repetition rate). For complex emissions, submit an exhibit describing in detail the modulating signal and indicate the frequency range that it is associated with. Exhibits may be entered immediately after submitting this form or later by selecting the "Add Attachments" option from this web site's menu. NOTE: When submitting this exhibit, please enter "MODULATING SIGNAL DESCRIPTION". in the exhibit description.
Morehead State University 21 M Space Tracking Antenna
ANTENNA DRAWING: Vertical profile sketch of total structure of the Morehead State University 21 M Space Tracking Antenna including supporting building, with heights in meters above ground for all significant features.
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Dimensions Reflector: 21 m (68.9 ft) Maximum vertical height above ground (apex of feed at 90 degrees elevation): 25.6 m (84 ft) Height to elevation axle: 14.17 m (46.5 ft.) Height to center of feed ring at 0 degrees pointing elevation: 14.17 m (46.5 ft.) Height of LER 3.08 m (10 .1 ft)
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Photograph of the Morehead State University Space Science Center 21
Meter Space Tracking Antenna September, 2007
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INITIAL DISTRIBUTION LIST
1. Defense Technical Information Center Ft. Belvoir, Virginia
2. Dudley Knox Library Naval Postgraduate School Monterey, California
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4. Lieutenant Colonel Terry Smith Naval Postgraduate School Monterey, California
5. Mr. Bob Broadston Naval Postgraduate School Monterey, California 6. Mr. David Rigmaiden Naval Postgraduate School Monterey, California
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Naval Postgraduate School Monterey, California
8. Director, Training and Education,
MCCDC, Code C46 Quantico, Virginia
9. Director, Marine Corps Research Center MCCDC, Code C40RC Quantico, Virginia 10. Marine Corps Tactical Systems Support Activity (Attn:
Operations Officer) Camp Pendleton, California 11. Head, Information Operations and Space Integration
Branch, PLI/PP&O/HQMC, Washington, DC
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12. Professor Dan C. Boger Naval Postgraduate School Monterey, California